Improvements in induction range analysis.

Rationale:
Uses range analysis while determining whether trip-counts
are "safe", which improves analysis of triangular loops.
Also implements more effective triangular loop analysis
by evaluating induction information only once and using
a top level hint (instead of the "iterative refinement"
that was used earlier). Also fixes analysis of triangular
trip counts that may wrap-around. All with tests.

Test: see induction_var_range_test/530-checker-loops*

BUG=27151190

Change-Id: I1877c8ce0c9a52005900eb9dfdbb1918df100278

1 files changed, 1 insertions, 1 deletions

diff --git a/compiler/optimizing/induction_var_analysis.h b/compiler/optimizing/induction_var_analysis.h
index f1965f07b2..7c74816c26 100644
--- a/compiler/optimizing/induction_var_analysis.h
+++ b/compiler/optimizing/induction_var_analysis.h
@@ -132,7 +132,7 @@ class HInductionVarAnalysis : public HOptimization {
                                  InductionInfo* a,
                                  InductionInfo* b,
                                  Primitive::Type type) {
-    DCHECK(a != nullptr);
+    DCHECK(a != nullptr && b != nullptr);
     return new (graph_->GetArena()) InductionInfo(kInvariant, op, a, b, nullptr, type);
   }